The present invention relates to a natural-frequency measurement device for measuring the natural frequency of a belt, and more particularly relates to a technique for improving the accuracy with which the natural frequency is measured.
Unless a belt which is used in a belt transmission system so as to be stretched between its pulleys were placed under appropriate tension during its operation, the belt would either transmit the rotational forces of the pulleys less efficiently or shorten its life by itself. To address this problem, a tension test has been conducted in this field to measure the tension of a belt for use in a belt transmission system and examine whether the belt is placed under appropriate tension.
In carrying out a tension test on a belt, a sonic belt tension measurement device is often used, because the device enables the tester to measure its tension by a simple and non-contact method.
A sonic belt tension measurement device includes a natural-frequency measurement device. The natural-frequency measurement device senses, through a microphone, the sound waves produced by a belt stretched between pulleys when the belt is excited, and measures the natural frequency of the belt based on the sound waves sensed through the microphone. The sonic belt tension measurement device is configured to calculate the belt tension, corresponding to the natural frequency measured by the natural-frequency measurement device, according to a predetermined formula (see, for example, Japanese Unexamined Patent Publication No. H06-137932).